FIG. 1 is a view showing the construction of a conventional surface-mount chip antenna 10.
As shown in FIG. 1, the conventional surface-mount chip antenna 10 includes a dielectric block 11 made of ceramic material or resin. The dielectric block 21 includes a ground electrode 14 formed on the first surface 12 thereof, a radiation electrode 18 formed on the second surface 13 thereof, and a feeding pattern 15 formed in a from a portion of the first surface 12 of the dielectric block 11 to a portion of one side of the dielectric block 11. The radiation electrode 18 is spaced apart from the feeding pattern 15 by a certain distance and is connected to the ground electrode 14 via two short circuit portions 16 and 17 that are respectively formed on two sides of the dielectric block 11. Furthermore, the radiation electrode 18 has a length of λ/4 at a resonance frequency.
The surface-mount chip antenna 10 described above forms a resonance circuit using capacitance between the ground electrode 14 and the radiation electrode 18 and the inductance of the radiation electrode 18, and adjusts the resonance frequency by coupling the radiation electrode 18 with the feeding pattern 15 using the capacitance between the feeding pattern 15 and the radiation electrode 18. However, there is a problem in that it is difficult to provide multi-frequency band communication service because an electrode appropriate to a specific resonance frequency is formed through a certain pattern-forming process and is then used for only a single frequency band composed of one usable frequency band.
FIG. 2 is a view showing the construction of a conventional ceramic chip antenna.
As shown in FIG. 2, the conventional ceramic chip antenna includes a chip main body 20 formed by stacking a plurality of green sheets, which are made of a ceramic dielectric material, a first helical conductor 21 formed in the chip main body 20 in a helical form, and a second helical conductor 22 disposed in parallel with the first helical conductor 21 in the chip main body 20 and formed in a helical form. The first helical conductor 21 is formed using a plurality of horizontal and vertical strip lines in a helical form, and the helical rotational axis A of the first helical conductor 21 is parallel to the bottom and side surfaces 23 and 24 of the chip main body 20 made of ceramic. In the same manner, the second helical conductor 22 is formed using a plurality of horizontal and vertical strip lines in a helical form, and the helical rotational axis B of the second helical conductor 22 is parallel to the bottom and side surfaces 23 and 24 of the chip main body 20.
In this case, the first and second helical conductors 21 and 22 are independently formed without being connected to each other, the helical rotational axes A and B of the conductors 21 and 22 are parallel to each other, and the strip lines and the via holes in the respective green sheets are three-dimensionally connected to each other through precise alignment so that the first and second helical conductors 21 and 22 are formed.
Furthermore, voltage supply terminals 25 are formed at respective ends of the helical conductors 21 and 22 protruding outside the main body 20. In this case, if voltage is applied to the helical conductors 21 and 22 through the voltage supply terminals 25, a problem occurs in that the helical conductors 21 and 22 resonate in two different frequency bands.
Although the conventional ceramic chip antenna described above has recently been developed to a level at which it is possible to contain the antenna in a mobile terminal in the form of a small-sized chip, there are problems in that the characteristics of the antenna vary due to sensitivity to external environment factors and it is difficult to provide multiple frequency band radio communication service.
FIG. 3 is a view showing the construction of a conventional wireless Local Network Area (LAN) multi-band antenna.
The wireless LAN multi-band antenna is based on a well-known technology for reducing the size of an antenna, and employs a meander line.
As shown in FIG. 3, a portion of the upper surface of an insulating substrate is patterned to be formed in the shape of a meander line 32. In this case, a resonance frequency is determined according to the length of the meander line 32. That is, resonance occurs at a lower frequency as the length of the meander line 32 increases. The meander line 32 is designed to correspond to a first frequency range.
A portion of the lower surface of the insulating substrate 31 is patterned to be used as a ground 34, and thus resonance is induced at a third frequency band (that is, a frequency band of 5.8 GHz). In this case, the values of a frequency bandwidth and a resonance frequency vary with the area of the partial ground 34, that is, the length and size of the partial ground 34. When the area of the partial ground increases, the resonance occurs at a relatively low frequency. In contrast, when the area of the partial ground decreases, the resonance occurs at a relatively high frequency. A dual band (2.4 GHz and 5.8 GHz) is realized using the meander line 32 and the partial ground 34 as described above, a back microstrip line 33 is attached above the partial ground 34 to increase the frequency bandwidth, and thus a broadband accommodating a second frequency (5.2 GHz) and the third frequency (5.8 GHz) is formed.
Although the conventional wireless LAN multi-band antenna described above is manufactured such that it can be provided in a mobile communication terminal, the amount of current flowing through the meander line and the back microstrip line is limited, so that problems occur in that the gain and radiation characteristics of the antenna are degraded.